Search

Background: Worldwide, the emergence of carbapenem-resistant enterobacterales (CRE) and carbapenem-resistant Pseudomonas aeruginosa (CRPA) is a global concern to public health as they are responsible for several serious infections that lead to elevated treatment expenses, prolonged hospitalization, and a higher mortality rate. Aims and Objectives: To detect Carbapenem resistance in Enterobacterales and Pseudomonas aeruginosa by phenotypic methods such as mCIM and eCIM. To determine synergism between Ceftazidime-Avibactum and Aztreonum in metallobetalactamase producing isolates. Materials and Methods: Total 217 isolates including enterobacterales and Pseudomonas aeruginosa from patient’s samples such as urine, pus, blood, wound swab, sputum, and ET tube were processed as per standard protocol during the study period from July 2023 to January 2024 at Calcutta National Medical College, Kolkata. Results: Resistance to carbapenem was observed in 110/217 (50.69%) isolates. Phenotypically, 99/110 (90%) produced metallo-β-lactamase and 11/110 (10%) produced serine carbapenemase by mCIM with eCIM test. MBLs producing organisms were most commonly isolated from blood culture samples. On an average, 76% of the MBL producing isolates shows positive synergy result to the combination of CZA+AT by disk elution method. Conclusion: eCIM and mCIM test was performed for identification of carbapenemase producing CRE and CRPA, which causes serious infection in patients with no definitive treatment. The combination of CZA-AT is a potential treatment option to manage CRE and CRPA-associated infections.

Background: Worldwide, the emergence of carbapenem-resistant enterobacterales (CRE) and carbapenem-resistant Pseudomonas aeruginosa (CRPA) is a global concern to public health as they are responsible for several serious infections that lead to elevated treatment expenses, prolonged hospitalization, and a higher mortality rate. Aims and Objectives: To detect Carbapenem resistance in Enterobacterales and Pseudomonas aeruginosa by phenotypic methods such as mCIM and eCIM. To determine synergism between Ceftazidime-Avibactum and Aztreonum in metallobetalactamase producing isolates. Materials and Methods: Total 217 isolates including enterobacterales and Pseudomonas aeruginosa from patient's samples such as urine, pus, blood, wound swab, sputum, and ET tube were processed as per standard protocol during the study period from July 2023 to January 2024 at Calcutta National Medical College, Kolkata. Results: Resistance to carbapenem was observed in 110/217 (50.69%) isolates. Phenotypically, 99/110 (90%) produced metallo-β-lactamase and 11/110 (10%) produced serine carbapenemase by mCIM with eCIM test. MBLs producing organisms were most commonly isolated from blood culture samples. On an average, 76% of the MBL producing isolates shows positive synergy result to the combination of CZA+AT by disk elution method. Conclusion: eCIM and mCIM test was performed for identification of carbapenemase producing CRE and CRPA, which causes serious infection in patients with no definitive treatment. The combination of CZA-AT is a potential treatment option to manage CRE and CRPA-associated infections. [ABSTRACT FROM AUTHOR]

AIM: We aimed to evaluate the effectiveness of a modified Carbapenem Inactivation Method (CIM) in detecting carbapenemase production among different clinical Enterobacteriaceae strains. BACKGROUND: Given the increasing prevalence of carbapenem-resistant Enterobacteriaceae, there is a critical need for rapid and effective diagnostic methods for carbapenemase activity. While the original CIM provides a cost-effective approach for phenotypic detection, its modifications could potentially increase diagnostic accuracy and speed. METHODS: We analyzed 122 rectal swab samples from hospitalized patients using both the original and modified CIM (mCIM). Initial screening was conducted using MacConkey agar containing 2 mg/L meropenem. Species identification was confirmed via MALDI-TOF MS, and carbapenem resistance was assessed using a meropenem disk. The mCIM involved incubating swabs directly in nutrient broth at 35-37°C for 24 hours, followed by exposure to a 10 µg meropenem disk for two hours. The disk was then placed on Mueller-Hinton agar seeded with carbapenem-susceptible Escherichia coli (ATCC 29522), where inhibition zones of ≤16 mm indicated carbapenemase activity (Figure 1). RESULTS: Out of 53 isolated Enterobacteriaceae strains, 26 were meropenem-resistant. The mCIM identified carbapenemase activity in 53.8% of these resistant strains and 51.8% of meropenem-susceptible strains. In contrast, the CIM detected carbapenemase in only 26.9% of resistant strains and 7.4% of susceptible strains (Figure 2, Table 1). CONCLUSIONS: Our study demonstrated that mCIM significantly improves the detection of carbapenemase in both resistant and susceptible Enterobacteriaceae, suggesting its potential to enhance clinical diagnostics and treatment strategies. Polymerase chain reaction testing is needed to validate the findings.

Background/purpose(s): The continuously increasing carbapenem resistance within Enterobacterales and Pseudomonas poses a threat to public health, nevertheless, the molecular characteristics of which in southern China still remain limited. And carbapenemase identification is a key factor in effective early therapy of carbapenem-resistant bacteria infections. We aimed to determine the molecular characteristics of these pathogens and compare commercial combined disc tests (CDTs) with the modified carbapenem inactivation method (mCIM) and EDTA-CIM (eCIM) in detecting and distinguishing carbapenemases using whole genome sequencing (WGS). Methods: A total of 78 Enterobacterales, 30 Pseudomonas were obtained from two tertiary hospitals in southern China. Susceptibility tests were conducted using an automated VITEK2 compact system with confirmation via the Kirby-Bauer method. The WGS was conducted on all clinical isolates and the molecular characteristics were analyzed by screening the whole genome sequences. CDTs with or without cloxacillin, mCIM, and eCIM, were performed and compared by taking WGS results as the benchmark. Results: A total of 103 carbapenem non-susceptible and 5 carbapenem susceptible bacteria were determined, with Klebsiella pneumoniae (42.7%), Pseudomonas aeruginosa (23.3%) and Escherichia coli (18.4%) being most prevalent. Carbapenemase genes were detected in 58 (56.3%) of the 103 carbapenem-non-susceptible clinical isolates, including 46 NDM, 6 KPC, 3 IMP, 1 IPM+VIM, 1NDM+KPC, and 1 OXA-181. Carbapenemase-producing isolates were detected more frequently in Enterobacterales (76.3%). Among K. pneumoniae, the major sequence types were st307 and st11, while among E. coli and P. aeruginosa, the most prevalent ones were st410 and st242 respectively. For carbapenemase detection in Enterobacterales, the mCIM method achieved 100.00% (95% CI, 92.13-100.00%) sensitivity and 94.44% (70.63-99.71%) specificity (kappa, 0.96); for Pseudomonas, detection sensitivity was 100% (5.46-100.00%), and 100% (84.50-100.00%) specificity (kappa, 0.65). Commercial CDT carbapenemase detection sensitivity for Enterobacterales was 96.49% (86.84-99.39%), and 95.24% (74.13-99.75%) specificity (kappa, 0.90); for Pseudomonas, carbapenemase detection sensitivity was 100.00% (5.46-100.00%) and 37.93% (21.30-57.64%) specificity (kappa, 0.04). When cloxacillin testing was added, CDT specificity reached 84.61% (64.27-94.95%). Conclusion: The molecular epidemiology of carbapenem-non-susceptible isolates from pediatric patients in Southern China exhibited distinctive characteristics. Both the mCIM-eCIM combination and CDT methods effectively detected and differentiated carbapenemases among Enterobacterales isolates, and the former performed better than CDT among Pseudomonas. [ABSTRACT FROM AUTHOR]

Objectives: Ceftazidime avibactam (CZA) is a drug used against carbapenemase producing Gram-negative bacterial infections. Avibactam (AVI) is a non-beta-lactam-beta-lactamase inhibitor which has no action against metallo-β-lactamase (MBL) enzymes. This inadequacy is counteracted by combining CZA with aztreonam (ATM). The present study aims to denote the in vitro susceptibility pattern of the CZA and CZA-ATM combination in our area. Materials and Methods: In this study conducted prospectively from January to June 2023, the samples growing Enterobacterales and Pseudomonas aeruginosa were proceeded for carbapenemase detection by phenotypic testing for EDTA carbapenem inactivation method and modified carbapenem inactivation method. The minimum inhibitory concentration MIC of CZA was determined by E-strip and interpreted as per clinical and laboratory standard institute (CLSI) guidelines, while synergy testing of CZA and ATM was performed using ATM discs. Statistical Analysis: All data were entered in Microsoft Excel and analyzed for basic statistics. Results: The study included 150 carbapenem resistant organisms (131 Enterobactarales and 19 P. aeruginosa). Among these Enterobacterale strains, 72 (54.9%) were MBL producers. CZA resistance was detected in 69.3% of Klebsiella spp., 61.53% of Escherichia coli , and 50% of Serratia spp. Among Klebsiella spp. and E. coli , 88.9% and 65.2% of MBL isolates showed in vitro synergy to CZA-ATM. Conclusions: The study highlights a good in vitro sensitivity pattern of the CZA and ATM combination. However, we also highlight a growing percentage of non-synergistic interactions that need further genetic evaluation. [ABSTRACT FROM AUTHOR]

Background: In the past decade, there has been a global emergence of carbapenem-resistant Gram-negative bacilli, especially Enterobacterales. Carbapenem resistance is attributed to the ability of the bacteria to produce carbapenemases. The aim of the study is to detect carbapenem-resistant Enterobacterales (CRE) in different clinical isolates and study carbapenemase production by phenotypic methods in CRE. Materials and Methods: A total of 379 Enterobacterales were isolated from different clinical samples from patients attending outpatient departments and admitted in wards and intensive care units (ICUs). They were tested for carbapenem resistance by Kirby–Bauer disk diffusion method and then tested for carbapenemase production by ethylenediaminetetraacetic acid (EDTA)–disk synergy test and Modified Carbapenem Inactivation Method (mCIM). Results: This study was conducted from February 2021 to August 2022. Out of 379 Enterobacterales, 70 (18.47%) were CRE, out of which maximum carbapenem resistance of 23.53% was shown by Klebsiella pneumoniae isolates. The maximum carbapenem resistance was seen in the age group of 16–45 years and the most number of CRE isolates were from ICUs. Phenotypic test results indicated that 54.28% (38/70) of isolates were positive for carbapenemase production by either of the phenotypic methods. Conclusion: About one-fifth of the Enterobacterales isolates were carbapenem resistant. This study highlights the use of phenotypic methods to detect carbapenemase production in CRE, which is responsible for multidrug resistance. This information is relevant for surveillance, to implement infection prevention and control practices and antibiotic policies.

Background: In the past decade, there has been a global emergence of carbapenem-resistant Gram-negative bacilli, especially Enterobacterales. Carbapenem resistance is attributed to the ability of the bacteria to produce carbapenemases. The aim of the study is to detect carbapenem-resistant Enterobacterales (CRE) in different clinical isolates and study carbapenemase production by phenotypic methods in CRE. Materials and Methods: A total of 379 Enterobacterales were isolated from different clinical samples from patients attending outpatient departments and admitted in wards and intensive care units (ICUs). They were tested for carbapenem resistance by Kirby--Bauer disk diffusion method and then tested for carbapenemase production by ethylenediaminetetraacetic acid (EDTA)--disk synergy test and Modified Carbapenem Inactivation Method (mCIM). Results: This study was conducted from February 2021 to August 2022. Out of 379 Enterobacterales, 70 (18.47%) were CRE, out of which maximum carbapenem resistance of 23.53% was shown by Klebsiella pneumoniae isolates. The maximum carbapenem resistance was seen in the age group of 16-45 years and the most number of CRE isolates were from ICUs. Phenotypic test results indicated that 54.28% (38/70) of isolates were positive for carbapenemase production by either of the phenotypic methods. Conclusion: About one-fifth of the Enterobacterales isolates were carbapenem resistant. This study highlights the use of phenotypic methods to detect carbapenemase production in CRE, which is responsible for multidrug resistance. This information is relevant for surveillance, to implement infection prevention and control practices and antibiotic policies. [ABSTRACT FROM AUTHOR]

Background: Carbapenems are among the last resorts in managing multidrug-resistant bacterial infections. The rise in resistance to carbapenems is a significant concern, and the production of carbapenemases that inactivate the drug is the most typical mode of resistance developed by the bacteria. Carbapenemase-producing bacteria are associated with higher morbidity and spread faster than noncarbapenemase-producing bacteria. Detection of carbapenemases is essential for epidemiological surveillance and in choosing the most efficient antimicrobial in managing the patient. Materials and Methods: We processed urine samples received in our laboratory over 6 months. Samples with carbapenem-resistant Enterobacterales were further processed for carbapenemase detection using the modified carbapenem inactivation method (mCIM), combined disc diffusion test (CDDT), Epsilometer test (E test), and modified Hodge test (MHT). The results were analyzed. Results: A total of 32.3% of Enterobacterales uropathogens showed resistance to imipenem/meropenem. The commonest isolate was Escherichia coli, followed by Klebsiella pneumoniae. Maximum positivity was detected by mCIM (89.2%) followed by CDDT (86.5%), E test (77.1%), and MHT (54%). Conclusion: In this study, we compared four phenotypic methods of carbapenemase detection and compared their diagnostic accuracy. These included CDDT, E test, MHT, and mCIM. Maximum positivity was detected by mCIM followed by CDDT and E test.

The prevalence of multidrug-resistant gram-negative bacilli has increased worldwide. Critical care areas of most hospitals use carbapenem antibiotics for the empirical treatment of gram-negative bacterial (GNB) infections. In the last decade, there have been reports of the detection of carbapenem-resistant Enterobacterales (CRE). This rise in the spread of CRE presents a great challenge in the treatment of GNB infections and poses a serious threat to global health. To detect the burden of CRE and to characterize CRE, we used three phenotypic methods for the detection of carbapenemase enzymes. Using conventional aerobic bacterial culture methods, 150 Enterobacterales strains were isolated from various clinical samples. Identification of CRE was performed using multiple phenotypic detection methods, such as the Kirby Bauer disc diffusion method for meropenem (10 mcg) using the CLSI 2021 interpretation for meropenem, modified Hodge test (MHT), Carba NP test, and modified carbapenem inactivation method (mCIM) test. A total of 150 Enterobacterales strains were isolated over a period of 1 year. Among these, 66/150 (44%), 63/150 (43%), 64/150 (43%), and 65/150 (43%) were identified as CRE using the Kirby Bauer disc diffusion method, MHT, mCIM test, and Carba NP test, respectively. The sensitivity and specificity of MHT, mCIM, and Carba NP tests within 95% CI were 93.94%/100%, 96.97%/100%, and 98.48%/100%, respectively. The positive and negative predictive values of MHT, mCIM, and Carba NP tests were 100%/95.45%, 100%/97.67%, and 100%/98.82%, respectively. The accuracies of the MHT, mCIM, and Carba NP tests were 97.33%, 98.67%, and 99.33% respectively indicating a high burden of carbapenem resistance in Enterobacterales. Therefore, given the current statistics of carbapenem resistance, use of carbapenem as empiric treatment in the intensive care units of hospitals may not be beneficial. Identification of carbapenem resistance can help in the initiation of appropriate antimicrobial therapy. This study compares the accuracy and efficiency of Carba NP, mCIM, and MHT in detecting carbapenem-resistant Enterobacterales.

We describe a case of carbapenem resistant E. coli isolated from urine in an 87-year-old woman with recurrent urinary tract infections. Using whole genome sequencing (WGS), we identified the carbapenem resistance mechanism to be a combination of ompC porin loss and plasmid-mediated AmpC gene blaCMY-2 , which was not detected by routine molecular and phenotypic carbapenemase assays. Our case raises a concern for the limitation of current CRE screening tools for emerging resistance mechanisms and demonstrates the utility of WGS as a better tool for characterization of CRE in the clinical setting.

The modified carbapenem inactivation method (mCIM) recommended by the Clinical and Laboratory Standards Institute is not applicable for detecting carbapenemases in Acinetobacter baumannii. Four currently reported phenotypic detection methods, namely, the modified Hodge test, the mCIM, the adjusted mCIM, and the simplified carbapenem inactivation method (sCIM), did not perform well in our 90 clinical A. baumannii isolates. Thus, the minimal inhibitory concentrations (MICs) of carbapenems and the existence and expression of carbapenemase-encoding genes were detected to explain the results. According to the E-test, which was more accurate than the VITEK 2 system, 80.0 and 41.1% were resistant to imipenem (IPM) and meropenem (MEM), respectively, and 14.4 and 53.3% exhibited intermediate resistance, respectively. Five β-lactamase genes were found, of which blaOXA-51-like, blaTEM, and blaOXA-23-like were detected more frequently in 85 non-susceptible strains. The expression of blaOXA-23-like was positively correlated with the MIC values of IPM and MEM. Therefore, an improved approach based on the mCIM, designated the optimized CIM (oCIM), was developed in this study to detect carbapenemases more accurately and reproducibly. The condition was improved by evaluating the factors of A. baumannii inoculum, incubation broth volume, and MEM disk incubation time. Obvious high sensitivity (92.94%) and specificity (100.00%) were obtained using the oCIM, which was cost-effective and reproducible in routine laboratory work.

There is an alarming rise in carbapenem-resistant Enterobacteriaceae (CRE) causing nosocomial infections such as ventilator-associated respiratory infections (VARIs). The use of rapid phenotypic methods for the detection and differentiation of carbapenemases elaborated by these CRE would be helpful in providing timely empirical therapeutic options for management of these infections and preventing spread of these CRE strains in hospital settings. Hence, this study aimed to detect CRE among pathogens isolated from the endotracheal secretions recieved from suspected cases of VARIs and differentiate carbapenemases elaborated by these CRE using combined phenotypic methods, such as the modified carbapenem inactivation method (mCIM) and EDTA modified CIM (eCIM). This observational study was conducted over a period of 1 year in the Department of Microbiology and the intensive care unit of a tertiary care center. Carbapenem resistance was found in 75% of Klebsiella pneumoniae isolates and 50% of Escherichia coli isolates, of which 58.4% were metallo-β-lactamases and 41.6% were serine carbapenemase producers. In conclusion, the combination of the mCIM and eCIM could be useful as an epidemiological tool and be considered essential in deciding the initial antibiotic therapy, help reduce morbidity and mortality associated with VARIs, and guide hospital infection control practices.

Background: Carbapenem-resistant Acinetobacter species have emerged as notorious pathogens causing nosocomial infections. Several phenotypic methods have been developed for detecting carbapenemase production in Enterobacteriaceae. The accuracy of these methods in the prediction of carbapenemase production in Acinetobacter species has not been studied well. Methods: This retrospective study enrolled adult patients with Acinetobacter bacteremia from four medical centers in Taiwan between 2012 and 2016. Their demographics and clinical outcomes were recorded. The carbapenem susceptibility of the Acinetobacter species was determined using the agar diffusion method. The carbapenemase genes were detected by PCR. Four phenotypic methods, including the modified Hodge test (MHT), modified carbapenem inactivation method (mCIM), Carba NP test, and CarbAcineto NP test were carried out to determine the production of carbapenemase. Results: We analyzed 257 adults who received initial carbapenem monotherapy for the treatment of Acinetobacter bacteremia. Shock within three days of bacteremia and acquisition of carbapenem non-susceptible isolates were independently associated with a higher 14-day and 30-day mortality in patients with Acinetobacter bacteremia. Among the four phenotypic tests for carbapenemase detection, MHT using the imipenem disc displayed the greatest sensitivity (94%; 95% confidence interval [CI], 89–97%) and specificity (81%; 95% CI, 73–88%) for predicting imipenem non-susceptibility. Conclusion: Carbapenem non-susceptibility and shock were independent risk factors for mortality in patients with Acinetobacter bacteremia. The MHT could predict the carbapenem susceptibility of Acinetobacter isolates. It is a cheap and quick assay, which could be applied in clinical practice.

The prevalence of multidrug-resistant gram-negative bacilli has increased worldwide. Critical care areas of most hospitals use carbapenem antibiotics for the empirical treatment of gram-negative bacterial (GNB) infections. In the last decade, there have been reports of the detection of carbapenem-resistant Enterobacterales (CRE). This rise in the spread of CRE presents a great challenge in the treatment of GNB infections and poses a serious threat to global health. To detect the burden of CRE and to characterize CRE, we used three phenotypic methods for the detection of carbapenemase enzymes. Using conventional aerobic bacterial culture methods, 150 Enterobacterales strains were isolated from various clinical samples. Identification of CRE was performed using multiple phenotypic detection methods, such as the Kirby Bauer disc diffusion method for meropenem (10 mcg) using the CLSI 2021 interpretation for meropenem, modified Hodge test (MHT), Carba NP test, and modified carbapenem inactivation method (mCIM) test. A total of 150 Enterobacterales strains were isolated over a period of 1 year. Among these, 66/150 (44%), 63/150 (43%), 64/150 (43%), and 65/150 (43%) were identified as CRE using the Kirby Bauer disc diffusion method, MHT, mCIM test, and Carba NP test, respectively. The sensitivity and specificity of MHT, mCIM, and Carba NP tests within 95% CI were 93.94%/100%, 96.97%/100%, and 98.48%/100%, respectively. The positive and negative predictive values of MHT, mCIM, and Carba NP tests were 100%/95.45%, 100%/97.67%, and 100%/98.82%, respectively. The accuracies of the MHT, mCIM, and Carba NP tests were 97.33%, 98.67%, and 99.33% respectively indicating a high burden of carbapenem resistance in Enterobacterales. Therefore, given the current statistics of carbapenem resistance, use of carbapenem as empiric treatment in the intensive care units of hospitals may not be beneficial. Identification of carbapenem resistance can help in the initiation of appropriate antimicrobial therapy. This study compares the accuracy and efficiency of Carba NP, mCIM, and MHT in detecting carbapenem-resistant Enterobacterales. [ABSTRACT FROM AUTHOR]

Introduction: Blood Stream Infections (BSI) in Intensive Care Unit (ICU) patients at initial stages are acute infections which might even become life threatening. In developing countries, increasing antimicrobial resistance and emergence of Extended Spectrum Beta-Lactamases (ESBL) and carbapenemase has also added an extra burden on physicians. Aim: To study the prevalence of emergence of ESBL and carbapenemase producing Gram Negative Bacteria (GNB) causing BSI in ICU patients. Materials and Methods: The present cross-sectional study was conducted on 1537 blood samples which were received in duration of two years from 2018 to 2020 in the Department of Microbiology, Maharishi Markandeshwar Institute of Medical Sciences and Research (MMIMSR), Mullana, Haryana, India from various ICUs. A 5-7 mL of blood was aseptically added to BACTEC bottles and bottles after proper labeling were inserted into the machine and incubated upto five days. 0.1 mL of broth from positively flagged bottles was cultured on Blood and MacConkey Agar. These plates were incubated at 37o C for 24 hours and processed as per standard microbiological procedures. Data was entered locally and calculated on the Microsoft Excel database. Results: Among 1537 samples, 263 (17.11%) samples were flagged positive by BACTEC system. On culture out of 263 samples, 51 (19.40%) were Gram Positive Cocci (GPC), 21 (07.98%) were Candida spp. and 191 (72.62%) were GNB. Among 191 Gram negative isolates, Escherichia coli 64 (33.51%) was the predominant organism followed by Klebsiella spp. 60 (31.41%). For all gram negative isolates, meropenem was the most sensitive drug followed by imipenem. Tigecycline (81.25%) was the second most effective drug against Acinetobacter baumannii. ESBL detection was done by Combine Disc Test on 124 samples (Escherichia coli and Klebsiella spp.) which showed Klebsiella spp. 25(20.16%) as the highest ESBL producing organism The rate of carbapenemase producer was 20 (10.45%) among all the gram negative isolates. Conclusion: For BSI in ICU patients, culture and sensitivity along with screening for prevalence of ESBL and carbapenemase producers should be done prior to starting antibiotics

Yunying Wang,1 Hui Liu,2 Lijun Zhang,1 Bin Sun1 1Department of Laboratory Medicine, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, People’s Republic of China; 2Department of Blood Transfusion, The First Affiliated Hospital of Chongqing Medical University, Chongqing, People’s Republic of ChinaCorrespondence: Bin SunDepartment of Laboratory Medicine, The Second Affiliated Hospital of Chongqing Medical University, No. 74 Linjiang Road, Yuzhong District, Chongqing, People’s Republic of ChinaTel +86 23-62887812Fax +86 23-63703244Email sunbin@cqmu.edu.cnPurpose: Infection and transmission of carbapenem-resistant Aeromonas is a serious threat to public health. Rapid and accurate detection carbapenem-resistant of these organisms is essential for reasonable treatment and infection control. This study aimed to find a simple and effective method to detect carbapenem-resistant phenotype in Aeromonas.Methods: A total of 131 clinical preserved Aeromonas strains were used in this study. The carbapenemase genes were detected by PCR. Modified carbapenem inactivation method (mCIM) in conjunction with EDTA-modified carbapenem inactivation method (eCIM) and simplified carbapenem inactivation method (sCIM) were performed to detect carbapenemases. We also designed a simple method, carbapenem inactivation method using supernatant (CIM-s), to detect the carbapenemase activity in the medium.Results: Of the 131 Aeromonas strains, 79 contained carbapenemase genes, including 68 blaCphA, 6 blaKPC-2, 2 blaNDM-1 and 3 blaKPC-2+CphA. However, routine antibiotic susceptibility testing could not completely identify carbapenemase-producing Aeromonas. In phenotypic assays, the sensitivity and specificity of mCIM were 100%. The combined mCIM and eCIM could distinguish serine carbapenemase and metallo-β-carbapenemases except co-producing organisms. The sensitivity and specificity of sCIM were 92.4% and 100%, respectively, which could not detect CphA totally. CIM-s results indicate that these carbapenemases could secrete into the medium to perform their hydrolytic activities and had a sensitivity and specificity of 97.5% and 100%, respectively.Conclusion: The combination of mCIM and eCIM can effectively detect and distinguish different types of carbapenemase in Aeromonas, and could be used as an important supplement approach to the antibiotic susceptibility testing.Keywords: Aeromonas, modified carbapenem inactivation method, carbapenemase, multidrug resistant, phenotypic detection

Introduction: Carbapenemase-producing Gram-negative bacilli are a worldwide problem, which represent a health concern because most of their resistance mechanisms are encoded by plasmids and therefore easily transmissible in hospital settings. Many methods have been proposed to detect such resistance, but screening is still challenging. Recently, the modified carbapenem inactivation method has shown promising results; however, more studies need to be performed. Hence, this study aimed to evaluate the performance of the mCIM in carbapenem-resistant Enterobacteriaceae and non-fermenting Gram-negative bacilli isolates. Materials and methods: From a microbial collection with molecular characterization of carbapenemase genes previously conducted, 100 Gram-negative bacilli isolates were selected: fifty-two non-carbapenemase-producing and 48 carbapene- mase-producing isolates. The mCIM was performed according to the CLSI guidelines, and to assess the performance of the method, sensitivity and specifi- city were calculated. Results: The sensitivity of the mCIM observed in this study was 96% (46/48), and the specificity was 96,2% (50/52). Most of the Gram-negative bacilli carrying a carbapenemase gene were mCIM-positive. Moreover, in carbapenem-resistant isolates that do not produce a carbapenemase (En- terobacteriaceae and non-fermenters), the results of the mCIM were negative. Conclusion: Overall, the mCIM provides a good alternative for the screening of carbapenemase-producing Gram-negative bacilli. Our findings highlight that mCIM is a sensitive and specific method to assess carbapenemase production in non-fermenting Gram-negative bacilli and Enterobacteriaceae such as Enterobacter cloacae. [ABSTRACT FROM AUTHOR]

There is an alarming rise in carbapenem-resistant Enterobacteriaceae (CRE) causing nosocomial infections such as ventilator-associated respiratory infections (VARIs). The use of rapid phenotypic methods for the detection and differentiation of carbapenemases elaborated by these CRE would be helpful in providing timely empirical therapeutic options for management of these infections and preventing spread of these CRE strains in hospital settings. Hence, this study aimed to detect CRE among pathogens isolated from the endotracheal secretions received from suspected cases of VARIs and differentiate carbapenemases elaborated by these CRE using combined phenotypic methods, such as the modified carbapenem inactivation method (mCIM) and EDTA modified CIM (eCIM). This observational study was conducted over a period of 1 year in the Department of Microbiology and the intensive care unit of a tertiary care center. Carbapenem resistance was found in 75% of Klebsiella pneumoniae isolates and 50% of Escherichia coli isolates, of which 58.4% were metallo-ß-lactamases and 41.6% were serine carbapenemase producers. In conclusion, the combination of the mCIM and eCIM could be useful as an epidemiological tool and be considered essential in deciding the initial antibiotic therapy, help reduce morbidity and mortality associated with VARIs, and guide hospital infection control practices. [ABSTRACT FROM AUTHOR]

In order to investigate the diagnostic performance characteristics of four phenotypic assays in detecting carbapenem-resistant Enterobacteriaceae (CRE), we collected the CRE strains from infected patients. The results of carbapenemase gene detection, bla KPC-2, bla OXA-23, bla NDM-1, bla NDM-4, bla NDM-5, bla IMP-4, and bla IMP-8, were used as a standard to evaluate the performances of combined disk test (CDT), modified carbapenem inactivation method(mCIM)/EDTA-modified carbapenem inactivation method(eCIM), NG-Test CARBA 5 (CARBA), and color developing immunoassay (CDI). The compliance of phenotype results based on CDT, mCIM/eCIM, CARBA, and CDI with genetic detection results was 94% (231/247), 95% (235/247), 98% (242/247), and 99% (246/247), respectively. CDT demonstrated a low specificity for carbapenemase detection, low negative predictive value (NPV), and low sensitivity for metallo-β-lactamase (79%, 55%, and 88%, respectively); it also failed to accurately detect IMP. The mCIM/eCIM assay had serious problems in detecting OXA-23-like carbapenemases. The sensitivity and specificity of CARBA and CDI were higher than those of the first two methods. However, CARBA did not cover the detection of OXA-23, while CDI cannot detect IMP-8, resulting in low NPVs (70% and 88%, respectively). In conclusion, CARBA and CDI assays are highly accurate except individual rare genes and allow direct genotype detections. CDT and mCIM/eCIM assays are moderately accurate and can only distinguish serine-β-lactamases from metallo-β-lactamases. Laboratories should choose the appropriate method that meets their needs based on its characteristic. [ABSTRACT FROM AUTHOR]

Objectives: Carbapenem-resistant Enterobacteriaceae (CRE) are a major public-health threat. The most important mechanism of carbapenem resistance in CRE is carbapenemase production. Early identification of carbapenemase-producing Enterobacteriaceae (CPE) leads to improved clinical outcomes. This systematic review aimed to assess the accuracy and applicability of the modified Hodge test (MHT), the carbapenemase Nordmann–Poirel (Carba NP) test, the modified carbapenem inactivation method (mCIM) and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF/MS) for CPE detection. Methods: The meta-analysis included pooled sensitivity, specificity, diagnostic odds ratio, and summary receiver operating characteristic (SROC) curve and area under the curve (AUC). Results: A total of 67 studies were included in the analysis. Pooled effect sizes (95% confidence interval) of the MHT, Carba NP, mCIM and MALDI-TOF/MS, respectively, were as follows: sensitivity, 92% (87–95%), 97% (94–98%), 99% (99–100%) and 99% (96–100%); specificity, 93% (86–97%), 100% (99–100%), 99% (96–100%) and 99% (96–100%); diagnostic odds ratio, 98.156 (48.175–199.995), 1277.710 (751.391–2172.692), 3597.352 (1287.575–10000) and 1781.360 (651.827–4868.228); and AUC, 0.97, 1, 1 and 1. Conclusion: Carba NP, mCIM and MALDI-TOF/MS all demonstrated high accuracy in CPE detection, whereas the MHT is not recommended owing to some clear drawbacks. We recommend the selection of carbapenemase detection tests in the order of mCIM, Carba NP and MALDI-TOF/MS according to their simplicity, cost, and equipment and skills involved.

Objective To evaluate the performance of modified carbapenem inactivation method (mCIM) and EDTA carbapenem inactivation method (eCIM) in detection of carbapenemase in Enterobacteriaceae Bateremia. Methods Polymerase chain reaction (PCR) was used to detect carbapenemase gene in 136 strains of carbapenem-resistant and -sensitive Enterobacteriaceae clinically isolated from 16 county-level hospital during January 2017 and September 2018. Meanwhile, the phenotype of obtained carbapenemase gene was screened by mCIM and eCIM. The results of gene detection and phenotypic screening test were analyzed and evaluated. Results Seventy-nine strains out of 85 carbapenem-resistant Enterobacteriaceae strains (CRE) were positive to carbapenemase gene by PCR, and 8 strains expressed class A and B carbapenemase gene, accounting for 10.13% (8/79). Seventy-eight strains of 85 CRE strains were positive detected by mCIM, and 44 strains were identified to be positive by eCIM among them. The carbapenem-resistant genes were not detected in the 51 carbapenem-sensitive strains by mCIM results. Screening the carbapenemase by mCIM had the sensitivity of 98.7% (95%CI: 92.2~99.9), the specificity of 100.0% (95%CI: 92.1~100.0), and the Kappa value of 0.985. When eCIM screened metallo-β-lactamase, the sensitivity was 85.7% (95%CI: 72.1~93.6), the specificity was 94.4%(95%CI: 80.0~99.0), and the Kappa value was 0.787. Screening serine carbapenemase, the sensitivity of eCIM was 89.5%(95%CI: 74.3~96.6), the specificity was 100.0%(95%CI: 90.6~100.0), and the Kappa value was 0.904. Conclusion Combination of mCIM and eCIM can screen carbapenemase-producing Enterobacteriaceae effectively. However, the sensitivity of the combined detection to screen metallo-β-lactamase will be reduced with the emergence of a large number of co-expressed class A and B carbapenemase-producing Enterobacteriaceae.

In order to investigate the diagnostic performance characteristics of four phenotypic assays in detecting carbapenem-resistant Enterobacteriaceae (CRE), we collected the CRE strains from infected patients. The results of carbapenemase gene detection, blaKPC-2, blaOXA-23, blaNDM-1, blaNDM-4, blaNDM-5, blaIMP-4, and blaIMP-8, were used as a standard to evaluate the performances of combined disk test (CDT), modified carbapenem inactivation method(mCIM)/EDTA-modified carbapenem inactivation method(eCIM), NG-Test CARBA 5 (CARBA), and color developing immunoassay (CDI). The compliance of phenotype results based on CDT, mCIM/eCIM, CARBA, and CDI with genetic detection results was 94% (231/247), 95% (235/247), 98% (242/247), and 99% (246/247), respectively. CDT demonstrated a low specificity for carbapenemase detection, low negative predictive value (NPV), and low sensitivity for metallo-β-lactamase (79%, 55%, and 88%, respectively); it also failed to accurately detect IMP. The mCIM/eCIM assay had serious problems in detecting OXA-23-like carbapenemases. The sensitivity and specificity of CARBA and CDI were higher than those of the first two methods. However, CARBA did not cover the detection of OXA-23, while CDI cannot detect IMP-8, resulting in low NPVs (70% and 88%, respectively). In conclusion, CARBA and CDI assays are highly accurate except individual rare genes and allow direct genotype detections. CDT and mCIM/eCIM assays are moderately accurate and can only distinguish serine-β-lactamases from metallo-β-lactamases. Laboratories should choose the appropriate method that meets their needs based on its characteristic.

Background Antimicrobial resistance has developed significant importance as a worldwide health concern more so in the 21 st century. This is more specifically observed among the Enterobacteriaceae family, the major group of Gram-negative bacteria. Resistance to carbapenems and colistin antimicrobials from the reserve group, in critical infection treatment poses a substantial therapeutic challenge. This study aims to detect resistance to both carbapenems and colistin in Enterobacteriaceae isolates, emphasizing the importance of monitoring. Materials and methods A laboratory-based study investigated 82 Carbapenem-Resistant Enterobacteriaceae (CRE) isolates from hospitalized patients at Krishna Hospital & Medical Research Centre, Karad, India, for two years (November 2021-November 2023). The Kirby-Bauer disc diffusion method was used to determine the antimicrobial susceptibility following Clinical Laboratory Standards Institute 2022 recommendations. To validate Carbapenem-Resistant Enterobacteriaceae isolates, the Modified Carbapenem Inactivation Method (mCIM) was used, and Colistin resistance was ascertained using Broth Microdilution Susceptibility Testing (BMD). Results Among 309 Enterobacteriaceae isolates, 82 (26.5%) exhibited carbapenem resistance, with 75 confirmed by Modified Carbapenem Inactivation Method (mCIM) testing. For patients in the age group 51-60 years (20%), with men being the most prevalent, the predominance of CRE isolates was from the Intensive Care Unit (44%), mostly from urine samples (34.6%). The most dominant CRE was Klebsiella pneumoniae (62.7%), followed by Escherichia coli (32%). Colistin resistance was found in 14 (18.7%) of CRE isolates, with the highest minimum inhibitory concentration (MIC) at 4 µg/mL (n=10) and 16 µg/mL (n=4). Colistin-resistant isolates (n=10) were sensitive to amikacin (71.4%) and resistant to many antibiotics. Conclusion The extreme rise of colistin-resistant cases among CRE in healthcare settings is a solemn alarm. Among the most effective treatments, aminoglycosides amikacin and netilmicin show the greatest sensitivity against these colistin-resistant CRE infections. The findings stress the difficulties in treating such infections and the dire need for solid antimicrobial stewardship and novel therapeutic strategies., Competing Interests: Human subjects: Consent was obtained or waived by all participants in this study. Animal subjects: All authors have confirmed that this study did not involve animal subjects or tissue. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2024, Hait et al.)

Carbapenem-resistant Enterobacterales, particularly those that produce carbapenemases, pose a significant public health concern due to very limited treatment options. The timely identification of carbapenemase-producing Enterobacterales (CPE) is essential for putting in place efficient infection control measures and selecting appropriate antimicrobial therapies, thereby improving the clinical outcome of the patient. The purpose of this systematic review is to compare the diagnostic accuracy and practicality between two phenotypic tests, namely the modified carbapenem inactivation method (mCIM) and carbapenemase Nordmann-Poirel (Carba NP) test, in detecting carbapenemase production by Enterobacterales and thereby aiding the clinician in making a decision to choose an appropriate test for their phenotypic detection. This systematic review involved combining sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), accuracy, diagnostic odds ratio with 95% confidence interval (CIs), Forest plot for sensitivity and specificity, and plotting suitable summary receiver operating characteristic curve with the area under the curve. Of the 20 studies included in this review, the overall effect sizes of Carba NP and mCIM with 95% CIs were as follows: sensitivity, 91% (86-96%) and 97% (95-99%); specificity, 93% (88-97%) and 97% (93-100%); PPV, 97% and 98%; NPV, 79% and 90%; accuracy, 93% and 97%; diagnostic odds ratio, 1487.8879 and 8527.5541; and AUC, 0.85 and 1, respectively. In conclusion, the mCIM method showed superior sensitivity (97%), specificity (97%), and accuracy compared to the Carba NP test in detecting carbapenemase production, even though both these methods had a few technical limitations. The Carba NP test is rapid, affordable, and dependable, whereas mCIM is more accurate and cost-effective but time-consuming. We propose that both tests can be reliably used for screening of carbapenemase production in Enterobacterales, as endorsed by the Clinical and Laboratory Standards Institute even in resource-limited clinical laboratories, in the order of prioritizing the mCIM method first and then followed by the Carba NP test when situation demands expedited results., Competing Interests: Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2024, Suriya R et al.)

Introduction: Blood Stream Infections (BSI) in Intensive Care Unit (ICU) patients at initial stages are acute infections which might even become life threatening. In developing countries, increasing antimicrobial resistance and emergence of Extended Spectrum Beta-Lactamases (ESBL) and carbapenemase has also added an extra burden on physicians. Aim: To study the prevalence of emergence of ESBL and carbapenemase producing Gram Negative Bacteria (GNB) causing BSI in ICU patients. Materials and Methods: The present cross-sectional study was conducted on 1537 blood samples which were received in duration of two years from 2018 to 2020 in the Department of Microbiology, Maharishi Markandeshwar Institute of Medical Sciences and Research (MMIMSR), Mullana, Haryana, India from various ICUs. A 5-7 mL of blood was aseptically added to BACTEC bottles and bottles after proper labeling were inserted into the machine and incubated upto five days. 0.1 mL of broth from positively flagged bottles was cultured on Blood and MacConkey Agar. These plates were incubated at 37oC for 24 hours and processed as per standard microbiological procedures. Data was entered locally and calculated on the Microsoft Excel database. Results: Among 1537 samples, 263 (17.11%) samples were flagged positive by BACTEC system. On culture out of 263 samples, 51 (19.40%) were Gram Positive Cocci (GPC), 21 (07.98%) were Candida spp. and 191 (72.62%) were GNB. Among 191 Gram negative isolates, Escherichia coli 64 (33.51%) was the predominant organism followed by Klebsiella spp. 60 (31.41%). For all gram negative isolates, meropenem was the most sensitive drug followed by imipenem. Tigecycline (81.25%) was the second most effective drug against Acinetobacter baumannii. ESBL detection was done by Combine Disc Test on 124 samples (Escherichia coli and Klebsiella spp.) which showed Klebsiella spp. 25 (20.16%) as the highest ESBL producing organism The rate of carbapenemase producer was 20 (10.45%) among all the gram negative isolates. Conclusion: For BSI in ICU patients, culture and sensitivity along with screening for prevalence of ESBL and carbapenemase producers should be done prior to starting antibiotics. [ABSTRACT FROM AUTHOR]

Copyright of China Tropical Medicine is the property of China Tropical Medicine Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The emergence and spread of carbapenemase-producing Enterobacterales (CPE) is a worldwide public health threat. Rapid and accurate detection of CPE is essential to prevent their dissemination within health care settings. The aim of this study was to evaluate the performance of CIM, mCIM and mCIM with ammonium bicarbonate (mCIM-A) methods by using different interpretation criteria for detection of carbapenemases. One hundred and fifty-three Klebsiella pneumoniae isolates previously characterized by molecular tests, including 133 carbapenemase producers and 20 non-carbapenemase producers, were collected in this study. CIM and mCIM tests were performed as described previously. mCIM-A by adding 50 mM ammonium bicarbonate to the bacterial suspension prepared in tryptic soy broth. The inhibition zone diameter of around meropenem disc was measured and interpreted as positive according to i) Pierce and colleagues (<19 mm), ii) EUCAST meropenem susceptibility breakpoint (<22). CIM, although seems to be good for carbapenemases other than OXA-48-like and NDM, is not satisfactory (42.3% and 83.4%, respectively) for those enzymes with any of the interpretation criteria. OXA-48-like and NDM were detected with a better performance (88.7% and 92.8, respectively) with mCIM when results were interpreted according to <22 mm zone diameter for OXA-48-like and NDM. The best results were obtained with mCIM-A using <22 mm criteria without any difference in the results of other enzymes and negative strains. Conclusions: mCIM-A method interpreted with <22 mm meropenem zone diameter seems to be preferable compared to CIM and mCIM. mCIM-A is simple and useful tool for identification of CPEs in clinical microbiology laboratories. [ABSTRACT FROM AUTHOR]

Background: The existing modified carbapenem inactivation methods (mCIMs) recommended by the CLSI for detecting carbapenemase production have not been applicable for Acinetobacter baumannii. We evaluated the influence of matrices used in mCIMs and CIMTris on the stability of the disks for detecting carbapenemase producers and suggested optimal mCIM conditions for detecting carbapenemase-producing A. baumannii. Methods: Seventy-three A. baumannii isolates characterized for antimicrobial susceptibility and carbapenemase encoding genes were tested for carbapenemase production using mCIM and CIMTris. The influence of the matrices (Tryptic soy broth [TSB] and Tris-HCl) used in these methods on the stability of the meropenem (MEM) disk was also evaluated. The mCIM conditions were adjusted to enhance screening sensitivity and specificity for detecting carbapenemase-producing A. baumannii. Results: The matrices had an impact on the stability of the MEM disk after the incubation period (two or four hrs). TSB nutrient broth is an appropriate matrix for mCIM compared with Tris-HCl pH 7.6, which leads to the loss of MEM activity in CIMTris. The sensitivity and the specificity of the optimal mCIM were both 100%. Conclusions: We established optimal mCIM conditions for simple, accurate, and reproducible detection of carbapenemase-producing A. baumannii. [ABSTRACT FROM AUTHOR]

Objective To analyze the combined application of modified carbapenem inactivation method (mCIM) test and EDTA-carbapenem inactivation method (eCIM ) test in the detection of carhapenem-resistant Enterobacteriaceae. Methods For 80 strains of Enterobacteriaceae with reduced sensitivity to carbapenems, the carbapenemase gene (blaK-PC, blaNDM, blaIMP, blaVIM) was detected by PCR. At the same time, mCIM test and eCIM test were used to detect the resistant phenotype of carbapenemase-producing Enterobacteriaceae. Using the carbapenemase gene test results as the gold standard, we calculated the sensitivity and specificity of the mCIM test for the carbapenemase-producing strain, and calculated the sensitivity and specificity of the eCIM test for metal-(β-lactamase and serine carbapenemase. Thus, the combined application efficiency of the mCIM test and the eCIM test in the detection of the resistant phenotype of the carbapenemase-producing Enterobacter was analyzed. Results Among the 80 strains, 59 were carbapenemase-positive strains, 57 of which were positive for mCIM test, and the sensitivity of the mCIM test for carbapenem-producing strains was 96. 6% (57/59) ; 21 were carbapenemase-negative strains and were negative for mCIM test, the specificity of the mCIM test for carbapenemase-producing strains was 100.0% (21/21 ). Thirty-three metal-(β-lactamase genes (blaNDM, blaVIM, blaIMP genes) were positive, of which 28 strains were positive for eCIM test, and the sensitivity of the eCIM test for the production of metal-β-lactamase strains was 84. 8% (28/33). Forty-seven strains of metal-(β-lactamase gene were negative, the results of eCIM test were all non-positive, and the specificity of the metal-(β-lactamase-producing strain detected by eCIM test was 100.0% (47/47). The 27 strains of serine carbapenemase (blaKPC gene) were positive, and the eCIM test results were negative. The sensitivity of the eCIM test for detecting serine carbapenemase was 100.0% (27/27 ). Fifty-three strains of serine carbapenemase were negative, of which 51 strains were non-negative, so the specificity of the serine carbapenemase strain detected by the eCIM test was 96.2% (51/53). Conclusion The combined experiments of mCIM and eCIM in detecting the resistant phenotype of carbapenem-producing Enterobacteriaceae have higher sensitivity and specificity. [ABSTRACT FROM AUTHOR]

This study reports the simplified carbapenem inactivation method (sCIM) to detect carbapenemase-producing gram-negative bacilli in a simple and accurate manner. This method is based on the modified carbapenem inactivation method (mCIM) with the improvement of experimental procedures. Instead of incubating the antibiotic disk in the organism culture media, the organism to be tested was smeared directly onto the antibiotic disk in the sCIM. For evaluating the sensitivity and specificity of the method, a total of 196 Enterobacteriaceae, 73 Acinetobacter baumannii, and 158 Pseudomonas aeruginosa isolates were collected. Polymerase chain reaction (PCR) was used to detect the carbapenemase genes. Phenotypic evaluations were performed using both the sCIM and the mCIM. PCR results showed that, of the 196 Enterobacteriaceae strains, 147 expressed the carbapenemase genes blaKPC−2 (58.5%), blaIMP−4 (21.8%), blaIMP−2 (2.0%), blaVIM−1 (6.1%), blaNDM−1 (10.2%), and blaOXA−48 (1.4%). sCIM results had high concordance with PCR results (99.5%) and mCIM results (100%) with the exception of one Klebsiella pneumoniae strain, which had an minimal inhibitory concentration (MIC) for imipenem of 0.25 mg/L. PCR demonstrated that 53 of the 73 A. baumannii isolates expressed the carbapenemase genes blaOXA−23 (98.1%) and blaVIM−2 (1.8%). sCIM and PCR results corresponded but all A. baumannii isolates were carbapenemase negative by the mCIM. PCR demonstrated that 25 of the 158 P. aeruginosa isolates expressed carbapenemase genes blaVIM−1 (52%), blaVIM−2 (8%), blaVIM−4 (36%), and blaIMP−4 (4%). sCIM results had high concordance with PCR results (100%) and the mCIM results (99.4%) with the exception of one P. aeruginosa isolate that expressed the blaVIM−4 gene. The sCIM offers specificity and sensitivity comparable to PCR but has the advantage of being more user-friendly. This method is suitable for routine use in most clinical microbiology laboratories for the detection of carbapenemase-producing gram-negative bacilli.

Introduction: Carbapenems have become one of the last resort of antimicrobials. But in last few years, Carbapenem Resistant Enterobacteriaceae (CRE) have been reported worldwide. Various phenotypic tests have been proposed for detection of carbapenemase activity including the newer modified Carbapenem Inactivation Method (mCIM) as advised by Clinical Laboratory Standard Institute (CLSI) 2017 guidelines. Aim: Detection of CRE from clinical specimens with new mCIM method and its comparative evaluation with phenotypic and genotypic methods. Materials and Methods: Study was conducted between January 2017 and December 2017 at KIMS, Karad. Total 66 CRE, isolated from 1634 clinical specimens and identified by VITEK 2 (Biomerieux, France) were included in the study. Phenotype screening was done by mCIM (CLSI 2017) method and was compared with Modified Hodge test (MHT) and Combined Disc Test (CDT) methods. Klebsiella pneumoniae ATCC BAA-1705 and Klebsiella pneumoniae ATCC BAA-1706 were used as positive and negative controls respectively. Molecular confirmation of these isolates for carbapenemase producing genes blaNDM-1, blaOXA-48, blaKPC was done by multiplex Polymerase Chain Reaction (PCR) study. Results: Klebsiella pneumoniae (n=35) outnumbered the other bacterial species among 66 CRE included in the study. mCIM was positive for 65 (98.48%) out of 66 isolates while MHT and CDT was positive for 50 (75.75%) and 59 (89.39%) of CRE isolates respectively. All the CRE isolates showed presence of at least one carbapenemase producing gene. Conclusion: The mCIM method is simple, less subjective, cost effective, reproducible and most sensitive method and plays important role in detection and prevention of spread of CRE, thereby, reducing morbidity and mortality, especially where there is lack of automation and molecular diagnostic facility. [ABSTRACT FROM AUTHOR]

We evaluated the effectiveness of carbapenem inactivation method (CIM) and modified CIM (mCIM). Our results indicated that mCIM with 4 h incubation improved sensitivity and specificity for detecting carbapenemase-producing Enterobacteriaceae compared to CIM. Additionally, we developed a sodium mercaptoacetate-combination method (SMA-mCIM) to detect metallo-β-lactamase (MBL) with high sensitivity and specificity. [ABSTRACT FROM AUTHOR]

Carbapenemase-producing Enterobacterales (CPE) have become a global health concern. Current molecular detection methods require special equipment and reagents. Thus, there is an urgent need for a highly sensitive, specific, and simple method for phenotypic detection of CPE in clinical microbiology laboratories. A simplified carbapenem inactivation method (sCIM) was recently reported. However, its utility for CPE detection has not been sufficiently evaluated to date. We evaluated the sCIM and compared it with the modified CIM (mCIM), using 133 CPE strains (producing IMP, 92; NDM, 11; NDM and OXA-48–like, 1; KPC, 13; OXA-48–like, 12; GES-24, 3; Nmc-A, 1) and 82 non-CPE strains (extended spectrum β-lactamase, 61; AmpC, 21). The sCIM was conducted by loading bacteria onto imipenem and meropenem disks. When imipenem disks with a 1+ bacterial load were used, the sensitivity and specificity of the sCIM were 97.0% and 100%, and those of the mCIM were 97.0% and 96.3%, respectively. The specificity of the sCIM decreased to 57.3% when the bacterial load on imipenem disks was increased to 2+. In contrast, when meropenem disks with a 1+ bacterial load were used, the sCIM had a lower sensitivity (78.2%) and an equivalent specificity (100%). When meropenem disks with a bacterial load of 2+ were used, the sensitivity and specificity of the sCIM increased to 96.2% and 93.9%, respectively. The diameter of the inhibition zone on meropenem disks was larger than that on imipenem disks, and the sCIM was less sensitive when meropenem disks were used. In addition, sCIM detection rates when using meropenem disks were particularly low for OXA-48–like producers (bacterial load 1+, 0/12; bacterial load 2+, 10/12). Our results indicate that the sensitivity and specificity of the sCIM was dependent on the bacterial load and that large bacterial loads led to false positives for AmpC and extended spectrum β-lactamase producers. Thus, the sCIM has high sensitivity and specificity for appropriate bacterial loads when imipenem disks are used. • Sensitivity and specificity of sCIM was dependent on the bacterial load • Large bacterial loads led to false positives for AmpC and ESBL producers • sCIM was more sensitive when imipenem disks were used [ABSTRACT FROM AUTHOR]

Introduction. Carbapenem resistant Enterobacterales (CRE) are one of the leading causes of systemic and nosocomial infections and are multidrug-resistant organisms producing different carbapenemases. There are many genotypic and phenotypic methods for detecting the carbapenemases; however, there is a limitation for each. Modified carbapenem inactivation method (mCIM) assay is a recent phenotypic method which has been published by the Clinical and Laboratory Standards Institute. Hypothesis / Gap Statement. mCIM assay could provide a reliable method for the detection of carbapenemases in CRE. Aim. Evaluation of the mCIM assay performance for the detection of carbapenemases in Enterobacterales and the identification of the common carbapenemase genes at Eastern Province of Saudi Arabia and Kingdom of Bahrain. Methodology. A collection of 197 non-duplicate carbapenem resistant Enterobacterales clinical isolates, were evaluated with the mCIM test comparing its performance to multiplex PCR. The minimum inhibitory concentration susceptibility testing was done by the Etest method for imipenem, meropenem, and ertapenem. Results. The sensitivity of the mCIM assay was 94 % (95 % CI, (89.3-97.1)). In Saudi Arabia and Bahrain, OXA-48 was the most prevalent carbapenemase gene followed by NDM. Coexistence of multiple carbapenemase genes is reported in eleven cases. Conclusion. These findings indicate that the mCIM test is a reliable and simple assay for detecting the activity of carbapenemase in Enterobacterales , especially in resource-limited laboratories.

Objective: The emergence of carbapenem-resistant Escherichia coli and Klebsiella species is a global threat. We aimed to compare two phenotypic methods and evaluate the genotypic method for the detection of beta-lactamases produced by E. coli and Klebsiella spp., Materials and Methods: One hundred and twenty-six E. coli and Klebsiella isolates were examined for phenotypic production of beta-lactamases by using disc diffusion, combined disc test (CDT) and modified carbapenem inactivation method (mCIM). All strains were also studied for the presence of various genes by polymerase chain reaction., Results: Out of 126 isolates, 96% of the isolates were extended-spectrum β-lactamase (ESBL) producers based on the presence of various ESBL genes. CDT method showed higher number of total (89%) carbapenemases in comparison to mCIM (81%). Among carbapenemases none of the isolates were Klebsiella pneumoniae carbapenemase producer by CDT, while 69% isolates were metallo-beta-lactamase (MBL) producers. Another method, mCIM/ethylene diamine tetraacetic acid mCIM showed 100% agreement for MBL detection. As regards, AmpC and class D carbapenemases; 0.04% and 16% positivity was detected, respectively, based on CDT method. Molecular analysis revealed 91% of the isolates harbouring carbapenemase genes. bla NDM was the most common gene detected followed bybla OXA-48 . Nine of the bla NDM -positive isolates also possessed bla OXA-48 gene., Conclusion: Our finding shows high percentages of ESBL and carbapenemases in E. coli and Klebsiella spp. Among phenotypic methods, CDT seems to be a better choice as prevalence of carbapenemases shows lots of variation in our country. For Class B enzymes, both CDT and mCIM/eCIM can be used in the routine laboratories., Competing Interests: None

The increase in carbapenemase-producing Enterobacterales (CPE), including metallo-β-lactamase (MBL) producers, is a severe global health concern. Thus, highly sensitive and specific methods for detecting MBL producers are needed. In this study, we tested the detectability of MBL-producing Enterobacterales against three types of MBL inhibitors (sodium mercaptoacetate, SMA; ethylenediaminetetraacetic acid, EDTA; and dipicolinic acid, DPA) used in combination with a modified carbapenem inactivation method (mCIM). These inhibitor-combination mCIMs were tested against 129 CPE (IMP, 93; NDM, 11; KPC, 13; NMC, 1; OXA-48, 11) and 75 non-CPE. For evaluation of MBL inhibitors, we used two concentrations for each of the three inhibitors: DPA (200 and 300 mg l - 1 ), EDTA (5 and 10 mM), and SMA (1500 and 3000 mg l - 1 ). The overall sensitivities of SMA, EDTA and DPA were 97.1-99.0 %, 81.7-99.0 % and 88.5-96.2 %, respectively. Moreover, each method showed high specificity (99.0-100 %). Although inhibitor-combination mCIMs were highly sensitive and specific for the detection of MBL producers, we found that sensitivity was dependent on the concentration of inhibitors.

The increase in the prevalence and impact of infections caused by carbapenemase-producing Enterobacteriaceae is a global health concern. Therefore, rapid and accurate methods to detect these organisms in any clinical microbiology laboratory, including those in resource-limited settings, are essential to prevent and contain their spread. It is also important to differentiate between serine- and metal-dependent carbapenemases elaborated by carbapenemase-producing isolates for epidemiologic, infection control and prevention, and therapeutic purposes. Here, we describe the development and evaluation of the EDTA-modified carbapenem inactivation method (eCIM), an assay for discriminating between serine- and metal-dependent (i.e., metallo-β-lactamases [MBLs]) carbapenemases when used in conjunction with the modified carbapenem inactivation method (mCIM). The eCIM had an overall sensitivity and specificity of 100% and was adopted by the Clinical and Laboratory Standards Institute as a method to use in combination with the mCIM to identify MBL-producing Enterobacteriaceae ., (Copyright © 2019 American Society for Microbiology.)

The rapid spread of multidrug-resistant Gram-negative organisms constitutes one of the greatest challenges to global health. While Gram-negative organisms have developed several mechanisms to avert the bactericidal effects of commonly prescribed antibiotic agents, the increasing prevalence of carbapenemase-producing organisms (CPO) is particularly concerning given the rapid spread of mobile genetic elements containing carbapenemase genes, the limited treatment options for infections caused by these organisms, and the high mortality rates associated with CPO infections. Understanding if an organism is carbapenemase producing and, if so, the class of carbapenemase(s) produced has treatment implications, as some agents preferentially have activity against specific carbapenemases. Furthermore, CPO disseminate between patients with greater ease than non-CP-carbapenem-resistant organisms and warrant more intensive infection control measures than would be employed in the absence of carbapenemase production. Phenotypic assays currently used in clinical practice to detect CPO consist of the following: (i) growth-based assays which measure carbapenem resistance based on organism growth in the presence of a carbapenem antibiotic (e.g., modified Hodge test and modified carbapenem inactivation method), (ii) hydrolysis methods which detect carbapenem degradation products (e.g., Carba NP test and matrix-assisted laser desorption-ionization time of flight mass spectrometry), and (iii) lateral flow immunoassays which detect carbapenemase enzymes through the use of specific antibodies. Although there is no single phenotypic test that meets all specifications of the ideal test, as we describe in this review, there are a number of tests that are user-friendly, affordable, accurate, and feasible for implementation in clinical microbiology laboratories of all sizes., (Copyright © 2018 American Society for Microbiology.)

The objective of this study was to evaluate the performance of four phenotypic methods in the detection of carbapenemase-producing Enterobacteriaceae (CPE) in China. We evaluated the performance of four carbapenemase detection methods, the modified Hodge test (MHT), the Carba NP test, the meropenem hydrolysis assay (MHA) with 1- and 2-h incubation, and the modified carbapenem inactivation method (mCIM) with meropenem, imipenem, and ertapenem, on 342 carbapenem-resistant Enterobacteriaceae isolates (CRE) in China. PCR was used as the gold standard. The 2-h-incubation MHA performed the best in carbapenemase detection (overall sensitivity, specificity, positive predictive value, and negative predictive value all 100%). Second was the Carba NP test, with a sensitivity of 99.6%. The 1-h-incubation MHA performed poorly in Klebsiella pneumoniae carbapenemase (KPC) detection (sensitivity, 71.3%). For mCIM, the best performance was observed with the meropenem disk. The MHT exhibited the worst performance, with a specificity of 88.8%. All assays except 1-h-incubation MHA, which failed to identify 68 KPC-2s, had a sensitivity of >98% in the detection of 172 KPCs. Likewise, all assays had a sensitivity of >95% in the detection of 70 class B carbapenemases, except for MHT (82.9%). The 2-h-incubation MHA significantly improved the accuracy in CPE detection compared with that for 1-h incubation and performed the best in the detection of class A and B carbapenemases. Our findings suggest that the MHA is the most practical assay for carbapenemase detection. For those who cannot afford the associated equipment, both the Carba NP test and mCIM are good alternatives with regard to the practical requirements of time and cost., (Copyright © 2018 American Society for Microbiology.)

Aim: To investigate the mechanism leading to in vivo carbapenem resistance development in Klebsiella pneumoniae., Methods: Carbapenemase was detected using the modified carbapenem inactivation method. β-lactamases resistant genes were identified by PCR and sequencing. Clonal relatedness was evaluated by random amplified polymorphic DNA and multiple locus sequence typing. The relationship between sequence typing and resistant genes was analyzed by using the chi-squared test., Results: All ST37 carbapenem-resistant isolates were bla OXA-1 positive and all ST37 carbapenem-sensitive isolates were bla OXA-1 negative at Stage I. A significant relationship between carbapenem resistance and bla OXA-1 was observed. The bla OXA-1 -positive rate was significantly higher in ST37 K. pneumoniae than others., Conclusion: This is the first study about the development of carbapenem resistance in vivo potentially mediated by bla OXA-1 in ST37 K. pneumoniae among neonates.